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Hello Guys! Last month, we studied some important things about gregorian modes. I hope that the last edition has been useful for you to understand all the stuff we are talking about.
As we studied all the gregorian scales and its positions on each key, now we´ll understand the harmonic possibilities on each context, which is, the chords that are part of each major and minor key. This is what we call “Tetrads derivated from major and minor scale”. Those harmonic possibilities are built with the seven tetrads derivated from each key structure. The relative minor key has the same chords as his relative major key, but the starting point of both (the 1st degree) is different. Obviously, this is valid only to major and minor scales, not harmonic or melodic minor scales, since these last two have different intervals and chord structures. I would like to mention that I will not write here about the harmonic possibilities based just in triads, since chords formed by three sounds are already implicit in the way that this subject is been boarded right here. We should just remember that when 7ths are included in chords, the tetrads on I and IV degrees are still identical, with 7M, however the V degree is different because this chord has 7m. The minor chords on II, III and VI degrees have 7m, therefore are identical, while VII degree is a half-diminished tetrad. However, although the I and IV degrees have the same tetrads, the scales used in such chords do not have to be the same ones. The same happens with II, III and VI degrees, that are minor chords with 7m, however the scales used on each chord should be different. Remember that I am always talking about a major scale context, but it´s easy to find the same situation on a natural minor scale context, where I, IV and V degress has the same chords, but different scales should be used over them. The same happens with III and VI degress. As it was said previously, there are other groups of harmonic possibilities, just like that originary from harmonic and melodic minor scales. Their structures will be analysed later. On the example 1 you can find the chords built with the C major scale, in example 2 you can find the chords built in A minor. In both cases the change of octaves happened to provide an easier chord´s view. When you build the chords of all other major and minor keys, you will find the same types of tetrads on each degree. Therefore, there is something which is considered of great importance: A good view of transposition of all musical elements, such as chords, scales and arpeggios. Obviously it requires a bit of practicing, but it is always an essencial tool for a good development of the musician. As an exercise, you can build chord groups of all other major and minor keys of the cicle of fourths and fifths (both cicles were studied last month). You should also analyse the chord progressions in exercises 2 and 3, indicating the degrees and scales which can be used on each chord, as it was showed in exercise 1.Doubts? Suggestions? Send an e-mail to: ivan@venegasmusic.com ! Hugs !
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